重组肝CYP3A4与CYP3A29细胞微粒体药物代谢动力学比较

目的 比较巴马小型猪CYP3A29和人CYP3 A4稳定表达重组肝癌细胞株微粒体的药物代谢特征,在分子水平为巴马小型猪作为临床前药物代谢实验动物提供科学依据.方法 以CYP3A特异性代谢底物硝苯地平、睾酮及其抑制药酮康唑为探针药物,将探针药物与重组CYP3A4、CYP3A29细胞微粒体在优化的微粒体浓度、药物浓度、孵育时间等条件下进行体外孵育,高效液相色谱法检测其药物代谢(抑制)动力学参数,并将二者进行比较分析.结果 巴马小型猪CYP3A29与CYP3A4在硝苯地平和睾酮代谢差异无统计学意义(P＞0.05).酮康唑的抑制活性为:当代谢底物为硝苯地平时,酮康唑对CYP3A29和CYP3A4的半数抑制浓度分别为0.090,0.132 μmol·L-1(P＜0.05);当代谢底物为睾酮时,酮康唑对CYP3A29和CYP3A4的半数抑制浓度分别为0.056,0.032 μmol·L-1(P＜0.05).结论 重组CYP3A29与CYP3 A4细胞微粒体对硝苯地平和睾酮活性差异不显著;酮康唑对重组CYP3A29与CYP3A4细胞微粒体硝苯地平和睾酮代谢活性有差异.     

CYP3A4基因多态性对药物代谢及其个体化给药的影响

CYP3A4是一种重要的药物代谢酶,参与多种药物的体内代谢,该酶的活性在不同的体内,种族和联用药物之间存在着明显的差异。本文综述了CYP3A4酶的基因多态性对药物代谢的影响,以期为指导临床合理用药打下理论基础,确保临床合理用药的安全性和有效性。     

CYP3A4代谢药物的特点及其多态性的研究现状

<正>CYP3A4参与50%以上临床用药的Ⅰ相代谢,酶结构中有变异区和稳定区来适应代谢需要,是许多药物相互作用的根源。对其底物、诱导剂和抑制剂的研究,为完善联合用药提供了理论依据。基因多态性是影响酶功能的重要因素,测定用药者的遗传变异将成为临床个体化治疗的趋势。CYP3A4基     

CYP3A4酶介导的人类药物代谢性别差异

药代动力学的性别差异是临床上药物疗效的重要影响因素。引起药代动力学性别差异的比较重要的分子因素包括药物代谢酶和药物转运体等。CYP3A4是人体含量最丰富的酶,具有广泛的代谢底物。大部分体内、外研究表明CYP3A4底物的代谢具有明显的性别差异,女性体内的代谢快于男性。该文系统综述人肝脏CYP3A4酶介导的药物代谢性别差异的研究进展。     

细胞色素P450—3A4相关的药物相互作用

目的：综述与细胞色素P4503A4相关的药物相互作用。方法：检索Medline和中国药学文摘。结果：发现多种由CYP3A4催化代谢的药物之间可以竞争药物代谢酶,引起药物相互作用,CYP3A4的抑制剂和诱导剂均可以抑制或诱导CYP3A4催化代谢的药物代谢。导致有益或不良的药物相互作用。结论：CYP3A4催化代谢的药物联合使用,特别是CYP3A4抑制剂与底物联合使用时,可能因为抑制了药物的代谢而导致严重的药物不良反应。     

金银花提取物及主要成分对药物代谢酶CYP3A4的活性抑制作用研究

目的:考察金银花提取物及其主要成分绿原酸、咖啡酸和芦丁对CYP3A4活性的抑制作用.方法:采用重组人CYP3A4孵育法,以咪达唑仑作为该酶的活性探针药物,采用液相色谱-质谱联用法(LC-MS/MS)测定代谢产物1′-羟基咪达唑仑的浓度,计算代谢产物的初始生成速度,比较加入待测药物和空白对照时代谢产物的初始生成速度.结果:金银花提取物、绿原酸、芦丁对该酶有抑制作用,IC50值分别为2.13 mg/mL、28.8 μmol/L和17.6 μmol/L,且金银花提取物和绿原酸对该酶的抑制作用不可逆,咖啡酸的抑制作用很弱,几乎不会导致药物相互作用.结论:金银花可能影响联合使用的CYP3A4的底物药物的代谢.     

肾移植病人中CYP3A4基因多态性对环孢素A代谢的影响

目的 用基因分析技术对CsA代谢酶CYP3A4进行基因分型,以阐述CYP3A4基因多态性对环孢素A代谢的影响及相互关系,从而预测血药浓度及安全性。方法 用聚合酶链反应结合限制性片段长度多态性分析法分别建立了CYP3A的CYP3A4基因亚型3个新突变点(CYP3A4~*4,~*5,~*6)的基因分型方法,并对中国肾移植人群进行基因分型,同时测定CsA及其代谢物浓度,以原形药与代谢物浓度的比值MR作为表型验证指标。结果CYP3A4~*4,*~5,*~6等位基因在中国肾移植人群中的突变率为:2/133,3/197,3/200。野生型病人中肝肾功能正常和异常者测得MR均值分别为0.47±0.13和0.82±0.21。3种突变型病人MR均值为0.90±0.30。结论CYP3A4~*4,~*5,~*6等位基因的存在有可能降低了药物代谢酶CYP3A4的活性,从而使环孢素A的代谢减慢。     

基于CYP3A4代谢的相关药物对口服避孕药的影响

自1960年避孕药被广泛使用开始,目前世界上采用避孕药进行避孕的妇女超过1亿.口服避孕药（oral contraceptives,OC）作为一种有效的避孕手段在避孕药销售市场上占有主导份额.OC除了作为避孕手段外,在临床上也作为很多疾病的治疗药物使用.     

五酯片提取物对人CYP3A4及CYP3A5重组酶活性的抑制作用及其机制

五酯片是临床上常用的护肝中药单方制剂,常被用来治疗各种原因引起的肝损伤。前期研究表明五酯片可通过抑制CYP3A从而升高移植患者、大鼠体内他克莫司、环孢素、紫杉醇等药物的血药浓度。CYP3A4和CYP3A5是CYP3A的两种重要亚型,但它们在催化活性及对抑制剂敏感性上表现不同。对CYP3A4和CYP3A5抑制作用的差异可能会导致不同的药物相互作用,这种相互作用的风险在体内可能会被进一步放大。可见,研究五酯片对CYP3A4及CYP3A5活性抑制作用的异同具有较好的临床治疗学及经济学意义。然而,目前尚未见五酯片对CYP3A4及CYP3A5活性的抑制作用及作用机制的相关研究。因此,本研究利用人重组CYP3A4 (recombinant human CYP3A4, rhCYP3A4)、人重组CYP3A5 (recombinant human CYP3A5, rhCYP3A5)考察五酯片提取物对CYP3A4、CYP3A5活性的影响及作用特征、机制。结果表明,五酯片提取物对CYP3A4、CYP3A5活性的抑制作用存在NADPH、预孵育时间及浓度依赖性;其与CYP3A4及CYP3A5的结合比较牢固,不...     

CYP3A4的配体结合机制

细胞色素P4503A4（CYP3A4）是药物研发过程中研究最多也最具挑战性的药物代谢酶。研究表明CYP3A4有一个活性极强的酶结合位点且具有多配体结合的可能性。     

PXR受体调控的CYP3A诱导及其在药物代谢中的重要意义

机体每日都要接触大量外源性化合物（xenobiotics），包括环境、饮食、药物中的各种成分，其中亲脂性化合物如果不能被及时代谢为极性化合物，就会在肝脏蓄积并影响机体正常生理功能，产生毒性甚至致癌。细胞色素P450（CYPS）属于血红素蛋白基因超家族，编码一系列代谢酶系统，参与各类不同结构亲脂性化合物的生物转化，增强代谢物水溶性，利于排出体外，     

CYP3A4和P糖蛋白与药物的肠道处置

肠CYP3A4介导的生物转化和P糖蛋白介导的药物主动泵出肠细胞是决定口服药物生物利用度的主要因素。有证据显示CYP3A4和P糖蛋白在小肠不是共同调节的,但两者在药物肠道处置中的协同作用已得到体外试验和动物体内试验的证实。进一步了解两者的相互作用有助于改善CYP3A4/P糖蛋白底物的生物利用度。     

Pregnane X receptor- and CYP3A4-humanized mouse models and their applications

Pregnane X receptor (PXR) is a pivotal nuclear receptor modulating xenobiotic metabolism primarily through its regulation of CYP3A4, the most important enzyme involved in drug metabolism in humans. Due to the marked species differences in ligand recognition by PXR, PXR-humanized (hPXR) mice, and mice expressing human PXR and CYP3A4 (Tg3A4/hPXR) were established. hPXR and Tg3A4/hPXR mice are valuable models for investigating the role of PXR in xenobiotic metabolism and toxicity, in lipid, bile acid and steroid hormone homeostasis, and in the control of inflammation.     

Functional characterization of 21 CYP3A4 variants on amiodarone metabolism in vitro

1. Cytochrome P450 3A4 (CYP3A4) is an important member of the cytochrome P450 enzyme superfamily, with 33 allelic variants reported previously. Genetic polymorphisms of CYP3A4 can produce a significant effect on the efficacy and safety of some drugs, so the purpose of this study was to clarify the catalytic characteristics of 22 CYP3A4 allelic isoforms, including 6 novel variants in Han Chinese population, on the oxidative metabolism of amiodarone in vitro.

2. Wild-type CYP3A4*1 and other variants expressed by insect cells system were incubated respectively with 10–500?μM substrate for 40?min at 37?°C and terminated at ?80?°C immediately. Then these samples were treated as required and detected with ultra-performance liquid chromatography-tandem mass spectrometry used to analyze its major metabolite desethylamiodarone.

3. Among the 21 CYP3A4 variants, compared with the wild-type, the intrinsic clearance values (V_max/K_m) of two variants were apparently decreased (11.07 and 2.67% relative clearance) while twelve variants revealed markedly increased values (155.20～435.96%), and the remaining of seven variants exhibited no significant changes in enzyme activity.

4. This is the first time report describing all these infrequent alleles for amiodarone metabolism, which can provide fundamental data for further clinical studies on CYP3A4 alleles.     

Development of template systems for ligand interactions of CYP3A5 and CYP3A7 and their distinctions from CYP3A4 template

Starting from established CYP3A4 Template (DMPK. 2019, and 2020), CYP3A5 and CYP3A7 Templates have been constructed to be reliable tools for verification of their distinct catalytic properties. A distinct occupancy was observed on CYP3A4-selective ligands, but not on the non-selective ligands, in simulation experiments. These ligands often invade into Bay-1 region during the migration from Entrance to Site of oxidation in simulation experiments. These results offered an idea of the distinct localization of Bay-1 residue on CYP3A5 Template, in which the Bay-1 residue stayed closely to Template border. The idea also accounted for the higher oxidation rates of CYP3A5, than of CYP3A4, of noscapine and schisantherin E through their enhanced sitting-stabilization. Typical CYP3A7 substrates such as zonisamide and retinoic acids took their placements without occupying a left side region of Template for their metabolisms. In turn, the occupancies of the left-side region were inevitably observed among poor ligands of CYP3A7. Altered extent of IJK-Interaction or localization of a specific residue at the left-side would thus explain distinct catalytic properties of CYP3A7 on Template. These data suggest the alteration of each one of Template region, from CYP3A4 Template, led to the distinct catalytic properties of CYP3A5 and CYP3A7 forms.     

In vitro/in vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humans.

We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CL(int)) for 4-hydroxylation and CYP3A4 content and between the CL(int) for alpha-hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CL(int) for CYP3A4 was about 2-fold higher than the CL(int) for CYP3A5 in the case of 4-hydroxylation. However, the CL(int) for CYP3A5 was about 3-fold higher than the CL(int) for CYP3A4 in the case of alpha-hydroxylation. The metabolic rates for 4- and alpha-hydroxylation increased as the added amount of cytochrome b(5) increased, and their maximum values were 3- to 4-fold higher than those without cytochrome b(5). The values of CL(int), in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CL(int) value (sum of 4- and alpha-hydroxylation) obtained using three human liver microsomal samples was 4-fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration-time curve (AUC) of alprazolam is reported to increase following co-administration of ketoconazole and the magnitude of the increase predicted from the in vitro K(i) values and reported pharmacokinetic parameters of ketoconazole was 2.30-2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73-1.79 vs 1.58-1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro/in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants.     

Pharmacokinetics of midazolam in CYP3A4- and CYP3A5-genotyped subjects

Objective We investigated whether differences in pharmacokinetics of midazolam, a CYP3A probe, could be demonstrated between subjects with different CYP3A4 and CYP3A5 genotypes.Methods Plasma concentrations of midazolam, and of total (conjugated + unconjugated) 1OH-midazolam, and 4OH-midazolam were measured after the oral administration of 7.5 mg or of 75 µg of midazolam in 21 healthy subjects.Results CYP3A5*7, CYP3A4*1E, CYP3A4*2, CYP3A4*4, CYP3A4*5, CYP3A4*6, CYP3A4*8, CYP3A4*11, CYP3A4*12, CYP3A4*13, CYP3A4*17 and CYP3A4*18 alleles were not identified in the 21 subjects. CYP3A5*3, CYP3A5*6, CYP3A4*1B and CYP3A4*1F alleles were identified in 20, 1, 4 and 2 subjects, respectively. No statistically significant differences were observed for the AUC_inf values between the different genotypes after the 75-µg or the 7.5-mg dose.Conclusion Presently, CYP3A4 and CYP3A5 genotyping methods do not sufficiently reflect the inter-individual variability of CYP3A activity.     

Human PXR-mediated transcriptional activation of CYP3A4 by ‘Fuzi’ extracts

Objective: This study focused on determining whether the ‘Fuzi’ (FZ) extracts from different extraction methods are related to pregnane X receptor (PXR) and cytochrome P450 3A4 (CYP3A4), and explore the mechanism.

Methods: FZ was extracted under various conditions, and the components were identified by Ultra Performance Liquid Chromatography/Quad Time of Flight Mass Spectrometry (UPLC/Q-TOF-MS). Annexin V-FITC and propidium iodide staining assays were used to measure the cell cytotoxicity of these extracts. Real-time PCR, western blot analysis and reporter gene assay were used to detect the expression changes of PXR and CYP3A4.

Results: FZ extracts were found to contain high levels of monoester-diterpene alkaloids (MDAs) and diester-diterpene alkaloids (DDAs). FZ extracts were cytotoxic. Interestingly, we found that FZ extracts and DDAs can induce the expressions of PXR and CYP3A4. And the MDAs can inhibit the expressions of PXR and CYP3A4.

Conclusion: Different extracts of FZ can induce the expressions of PXR and CYP3A4 in different degrees. This may be related to the drug-drug interactions.     

Potent mechanism-based inhibition of CYP3A4 by imatinib explains its liability to interact with CYP3A4 substrates

BACKGROUND AND PURPOSE

Imatinib, a cytochrome P450 2C8 (CYP2C8) and CYP3A4 substrate, markedly increases plasma concentrations of the CYP3A4/5 substrate simvastatin and reduces hepatic CYP3A4/5 activity in humans. Because competitive inhibition of CYP3A4/5 does not explain these in vivo interactions, we investigated the reversible and time-dependent inhibitory effects of imatinib and its main metabolite N-desmethylimatinib on CYP2C8 and CYP3A4/5 in vitro.

EXPERIMENTAL APPROACH

Amodiaquine N-deethylation and midazolam 1′-hydroxylation were used as marker reactions for CYP2C8 and CYP3A4/5 activity. Direct, IC₅₀-shift, and time-dependent inhibition were assessed with human liver microsomes.

KEY RESULTS

Inhibition of CYP3A4 activity by imatinib was pre-incubation time-, concentration- and NADPH-dependent, and the time-dependent inactivation variables K_I and k_inact were 14.3 µM and 0.072 min⁻¹ respectively. In direct inhibition experiments, imatinib and N-desmethylimatinib inhibited amodiaquine N-deethylation with a K_i of 8.4 and 12.8 µM, respectively, and midazolam 1′-hydroxylation with a K_i of 23.3 and 18.1 µM respectively. The time-dependent inhibition effect of imatinib was predicted to cause up to 90% inhibition of hepatic CYP3A4 activity with clinically relevant imatinib concentrations, whereas the direct inhibition was predicted to be negligible in vivo.

CONCLUSIONS AND IMPLICATIONS

Imatinib is a potent mechanism-based inhibitor of CYP3A4 in vitro and this finding explains the imatinib–simvastatin interaction and suggests that imatinib could markedly increase plasma concentrations of other CYP3A4 substrates. Our results also suggest a possibility of autoinhibition of CYP3A4-mediated imatinib metabolism leading to a less significant role for CYP3A4 in imatinib biotransformation in vivo than previously proposed.